Indicating device



March 21, 1933. C GREEN 1,902,497

INDICATING DEVICE Filed April 26, 1930 Inventor'- Charles F." Green, by His Attorney.

Patented Mar. 21, 1933 CHARLES 1?. cam, 01' mi, m YORK, ABSIGNOB '10 0mm IL comm, AUORPOM'L'IOH GI HI'WYORK PATENT. OFFICE" mmaame n'avrca Application filed April 88, 1000. In tial Io. 7,716.

This invention relates to indicating devices and more particularly to indicating devices in which a movably mounted indicating member is immersed in a damping liquid;

and has for an object the rovision of a rigid, light and eflicient in 'cating member having improved indicating markings thereon.

The invention has particular application to magnetic compasses in which the card member or rose is immersed in a suitable damping liquid and has for a further object the provision of means for improvin the damping of the movement of the card in the li uid without adding to its weight.

n carrying the invention into effect in one form thereof I cut away or otherwise remove the major ortion of the body of the indicatin mem r to leave solid markings and gra uations attached to a supporting portion of the body, but having the greater portion of their outlines separate therefrom.

In illustrating the invention in one form thereof I have shown it as embodied in a magnetic compass but it is to be understood that the invention is ap licable to other indicating devices in who the movable indicating member is immersed in a' liquid medium.

For a better and more complete understanding of the invention reference should now be had to the following specification and the accompanying drawing in which Fig. 1 is an enlarged view of a compass card embodying the invention and Fig. 2 is an elevation partly in section of a magnetic compass in which the card of Fig.1 is used as the indicatin member.

Referring now to the drawing the card 10 is constructed of any suitable material and is preferably made in the form of an inverted cup having a top portion 11 and a cylindrical side Wall 12. Quadrantal segments of the top portion are cut away or otherwise removed to provide a supporting member comprising the rim 13 and the spider 14.

The major portion of the side wall is also cut away as shown to leave suitable compass markings shown as comprising the solid letters'15, digits 1e and intermediate gradua tions comprising teeth-like projections 17 arranfied in spaced apart relationship and suspen ed from the upper su porting rim" 13. Althou h not essential'to t e invention the digits 16 and grdduations 17 are arranged in spaced apart relationship with respect to each other and-are circumferentially disposed with r ct to a central axis. It is to be observed t at although the indicating markings comprising the letters 15, digits 16 and graduations 17 are attached 'to the'su porting rim 13, that the majorportion of ti: lines is separate therefrom.

The material from which the card 10 is fabricated is preferably a thin lig ht wei ht. metal substance such-for example as t in sheet co per or aluminum but may also be made 0 non-metallic materials such for exam le as celluloid.

Alt ough any suitable method may be employed to form the card 10, this is preferably ters. When this method is employed the portions of the blank which are to remain as solid indicating characters are coated with lithographing ink and the blank is then placed in an acid bath and left until the bare portions of the blank have been cut away due to the chemical action of the acid.

The card 10 may also be formed by any of the We l-known methods of electro-deposition. In forming the card with its solid markings by the methods of electro-deposition it has been found to be very satisfactory to employ a molybdenum blank having its surface recessed to correspond tothe cut .55 side we 12 may also be cut away to leave a air outblank inverted cup to leave the solid characy portions of the card; fill' the recreases with a suitable material sue for exsample as varnish or a compound and then (depositing pure metal such for example as prime copper from a copper sulphate bath. 'ilihe metal will preferably be deposited to a tilliilikness of between 5 and mils and may dihen be easily stripped from the matrix and ttheimatrix used over again for the formation cfiiother cards.

lDue to the unequal masses of material in tfilre digits and letters which are distributed vnircumferentially about the central axis, the teard would be statically unbalanced with re- -spect to the central axis if special precautions were not taken to balance the card. In order {to provide a balanced card the quadrantal asegments which are removed from the top ."surface 11 of the card are so designed that the unasses of the remaining supporting rim 13 and the spider 14 together with the masses of tthe solid markings of the compass card form the above described manner have the fur fther advantages of strength, rigidity and minimum weight.

When the invention is embodied in a com= pass a needle pointed pivot 19 made of a re- :fractory material is secured in the central @aperture 20 of the card ill by any suitable itastening means. The card is supported as shown in Fig. 2 by means of a central post 21 which is provided at one extremity with a jeweled bearing 22 in which the pivot 19 is journaled. An outer wall or casing 23 deffines a spherical bowl or chamber in which is contained a suitable damping liquid 24 such for example as alcohol. The front face of :the bowl is cut away to provide an opening 01 window through which the markings on the card 10 may be viewed by the observer.

ground glass lens 25 is secured in the win- -;dow and its surface is provided with a ver- 'Ttically disposedlubberine 26 which cooper- ;ates with the solid markings on the card it? to indicate the angular relationship between zithe lubber-line and the north-south axis of the earths magnetic field. When in use a compass, the card 10 will, due to its frictionslicontact with the liquid 22, be deflected from )its normal position to the earths magnetic it'ield whenever the angular position of the lhody upon whlch it is mounted changes.

meager When the deflecting force has ceased the card will seek to return and in so doin will swing past its normal position and fine y will come to rest in a true north-south position after a series of oscillations of ever diminishing magnitude. The greater the amount by Wl'llCh the card swings past its normal position and the greater the number of oscillations of the card before it comes to rest the more unsatisfactory is the compass from the point of view of the navigator.

Due to the additional friction resulting from eddies caused by the movement of the solid markings through the damping liquid, cards constructed in accordance with my invention have very superior damping characteristics. For example, I have found that the amount by which the card swings past the normal after a given deflection is only about one-half as great as that for smooth cards not constructed in accordance with the invention. Accordingly the number of oscillations required forthe card to come to rest is very greatly reduced. Thus, the navigator is able to bring the craft back to its true course or to change from one course another in very much less time than would otherwise be required.

Although in accordance with the provisions of the patent statutes I have described the invention as embodied in concrete form I would have it understood that the elements shown in the drawing are merely illustrative' and thatthe invention is not necessarily limited to the exact forms shown since alterations and modifications will readily suggest themselves to persons skilled in the art without departing from the true spirit 7 of this invention or from the scope of the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A com ass card comprising a central spider mom r, a circumferential rim portion attached to said spider, solid cardinal reference characters attached to said rim but having the major portion of their outlines separate therefrom, and intermediate grad-' nations comprising teeth attached to said rim and projecting therefrom.

2. A compass card comprising a centralsupporting spider provided with a circular rim portion, solid reference characters attached to said rim but having the major portion of their outlines separate therefrom, a second rim attached to said reference character, and intermediate reference graduations comprising a plurality oitceth arranged in spaced apart relationship and attached to one of said rims.

3. An indicating member comprising a cupped member having the major portion of its side wall cut away to provide a plurality of solid spaced apart markings of difierent masses circumferentially arranged "-1 its mass unevenly-distribute with respect to a central axis, and a supand having with respect to said central axis to form with said markings a balanced structure with respect to said central axis.

4. An indicating device comprising in comport attached to said markings bination, a wall defining a chamber, a fluid medium in said chamber, a supporting member movably mounted in said medium and means comprising solid indicatinfilcharacters 

